The research, done by Dave Fielder at the Michigan Department of Natural Resources, "clearly establishes" that trends in cormorants most account for the collapse of the perch fishery there, according to the Journal of Great Lakes Research.

The DNR study says that, from 1980 to 2004, cormorant populations soared from zero to about 14,000 birds. Fielder examined trends in perch reproduction, weather variables, water levels and fishing activity and found that "none of those factors were as influential as cormorant predation in contributing to the collapse of the perch population," according to the journal.

As if the Great Lakes needed another invader, here comes the Asian fish tapeworm, also featured in the latest issue of the journal.

The parasite can be deadly for fish, from minnows to carp and bass. And get this: Climate change may help promote expansion of the tapeworm, already found in the Detroit River.